In many applications, semiconductor devices have to be equipped with a reverse voltage protection. In unprotected devices, the supply voltage can be shorted by the substrate diode of the semiconductor chip. Considering a MOSFET as an example, a substrate diode can be formed by the pn-junction between a p-doped substrate and an n-doped drain zone located adjacent to the substrate in an epitaxial layer which has been deposited onto the substrate. In order to inhibit such short circuits, the substrate can be isolated during reverse voltage operation. As a consequence, the potential of the substrate is floating and undefined, i.e., the potential of the substrate depends on the state of other components integrated in the same substrate. A floating substrate entails the risk of a latch-up of parasitic thyristor structures inherent in many integrated circuits.
There is a general need for an integrated circuit arrangement which is capable of withstanding a certain reverse voltage without the risk of a high current flow and a latch-up due to parasitic semiconductor structures.